This application relates to systems and methods for implanting devices such as replacement heart valves, valve repair devices such as clips, stents, and similar therapeutic devices within the anatomy of a patient.
It is well known in the art to implant devices such as replacement heart valves, valve repairing clips, stents, reinforcement rings, and the like into the human heart to restore its function. Similar devices are also introduced into other parts of the human anatomy where mechanical repair is needed. Many such repair operations are carried out by first inserting a steerable delivery catheter by minimally invasive means into a desired organ of the human anatomy. Thereafter, a repair device positioned on the distal tip of a delivery element is passed through an internal lumen along the entire length of the delivery catheter until the repair device reaches the target organ, and the device is pushed out of the distal end of the catheter for implantation. Such repair devices may expand to assume a new shape once they are pushed out of the delivery catheter, some by means of self-expansion, others by means of mechanical expansion via balloons, expanders, actuators, and the like.
One of the problems confronted by such systems known in the art is that the steerable delivery catheter (also referred to as a steerable sleeve, or steerable guide catheter) may require to be threaded through a tortuous series of twists and turns through one or more lumens in the patient's anatomy. Once the delivery catheter is in position, the repair device at the tip of a delivery element must be pushed up, in a manner controlled from outside the patient, through a lumen of this tortuously twisted delivery catheter. When a normally straight delivery element is advanced through this curved sleeve with an implant at its distal tip, substantial bending forces develop between the sleeve and the delivery element, which results in substantial rubbing and friction between the delivery element and the curved steerable sleeve. This buildup of friction is problematic and, when twisting the proximal handle, only a portion of torque is likely to transmit to the distal end of the delivery element. Further, the transfer of this torque is irregular and requires “Dottering” (named after pioneer interventionalist Dr. Charles Dotter) to release stored torque as the system sticks and slips. As a result of this cumbersome transfer of torque through the system, an operator has a difficult time rotating the medical implant device at the tip of the delivery system with the degree of accuracy needed to efficiently position the repair device without overshooting. In terms of design, the delivery element must be stiff enough to transmit torque; however, it must also be flexible to avoid accumulating bending forces that result in friction loss.
By way of more detailed description, and referring to FIG. 1, there is shown a schematic frontal illustration, looking posteriorly from the anterior side of a patient 100. The heart 102 is a pump, the outlet of which is the aorta, including the descending aorta 104, which is a primary artery in the systemic circulation. The circulatory system, which is connected to the heart 102 further comprises the return, or venous, circulation. The venous circulation comprises the superior vena cava 108 and the inferior vena cava 106. The right and left jugular veins, 110 and 112, respectively, and the subclavian vein 114 are smaller venous vessels with venous blood returning to the superior vena cava 108. The right and left femoral veins, 116 and 118 respectively, return blood from the legs to the inferior vena cava 106. The veins carry blood from the tissues of the body back to the right heart, which then pumps the blood through the lungs and back into the left heart. The arteries of the circulatory system carry oxygenated blood (not shown) from left ventricle of the heart 102 to the tissues of the body.
FIG. 2 (prior art) shows that a vascular introduction sheath 204 has been inserted into the right femoral vein 116 via a percutaneous puncture or incision. A guidewire 200 has been inserted through the introduction sheath 204 and routed up the inferior vena cava 106 to the right atrium 202, one of the chambers of the heart 102. In this illustration, the left anatomical side of the patient 100 is toward the right. The guidewire 200 has been placed so that it can be used to track a delivery catheter into a region of the heart 102.
FIG. 3 (prior art) shows how, after the placement of a guidewire 200 into the left atrium of the patient's heart by known means, a delivery catheter 700, or sleeve, having an open central bore 704 may be advanced over the guidewire until a distal tip of the guide catheter is positioned in the left atrium. The purpose of the delivery catheter 700 shown in FIG. 3 is to permit a delivery element to advance and introduce a tool such as a clip, stent, valve, or the like, via a central bore of the guide catheter, into the left atrium for eventual placement in the heart via a puncture in the septum 504, for example, into the mitral valve 510. Tools such as these are typically introduced at the distal end of an delivery element. FIG. 3 shows the extremely tortuous radius of a guide catheter, through which a delivery element must be forced axially, and made to rotate while being forced axially.
For the most tools, accurate translational and rotational positioning and control are vital to procedural success, so attempts have been made to torsionally stiffen the delivery catheter to more reliably transmit torque from the proximal handle to the distal tip of the catheter. Unfortunately, conventional designs that aim to torsionally stiffen the delivery element naturally also increase the bending stiffness and thus increase friction interactions between the delivery catheter and sleeve. This potentially worsens the problems associated with friction buildup, such as stored torque, and poor transfer of torque. If a device is interacting with delicate anatomic structures, such as valve leaflets, friction-induced motion instabilities may lead to unintended injury or sub-optimal device placement.
Therefore, due to the problems described above, it is desired to have a delivery element that is reasonably easy to construct and that can transfer maximum torque, while also having minimum bending stiffness. The present invention addresses these and other needs.